The analysis of land-cover change in the Berg River catchment has revealed notable changes occurring in various portions of the catchment. However, many questions are posed by the result presented in the preceding chapter. This section suggests avenues for further study.
As noted in preceding sections, significant areas of re-established Hopefield Sand Fynbos were registered in the change analysis. A detailed assessment of this vegetation type that measures species diversity between different areas of natural vegetation would contribute significantly toward an assessment of biodiversity in this area. Pivotally, the status of reclaimed areas of Hopefield Sand Fynbos in terms of species composition and diversity should be established as this would provide a good indication of the prospects for species associated with this vegetation type. Such research could contribute significantly toward the sustainable management of this area.
Significant reductions in cultivation were evident over the study period. While the degree to which this is indicative of genuine large-scale changes in agricultural practices is questionable, it is clear that undocumented changes are taking place. Various explanations for the changes have been offered ranging from a decreasing watertable to the intensification of centre-point irrigated potato cultivation (Helme pers com 2011). However, no satisfactory explanations have yet been found. As shifts in agricultural practice have far-reaching consequences for biodiversity as well as economic activity in this area, assessment of agricultural changes should be undertaken to determine whether the trends described in this study are authentic, what is driving them and their potential implications for the sustainable management of the Berg River catchment.
Large-scale removal of commercial forestry in and around the headwaters of the Berg River was revealed by this study. Some work has been done on the capacity of indigenous vegetation to re- establish following the removal of commercial forestry, but little has focused on the current state of the areas which have been cleared. This study advocates a detailed assessment of the compositional diversity of re-established fynbos and renosterveld vegetation types in denuded plantations. As the WfW programme has prioritized the removal of alien trees in riparian areas of the Berg River catchment, the status of these areas following the removal of alien vegetation should be assessed as well.
Invasive alien vegetation poses one of the single greatest threats to indigenous biodiversity in the CFR. It is hence a pivotal and pressing concern that the invaded areas be identified and contained. Direct measures of mapping alien vegetation are time-consuming and, given the scale of the problem, are unlikely to offer an effective solution. Rouget et al. (2004a) have modeled the potential range of invasive alien plant species in accordance with environmental characteristics to streamline further research and clearing efforts. However, this approach fails to give an indication of actual invasions and does not adequately address the problem. Data
concerning the distribution of alien vegetation in South Africa are at a very coarse scale and impractical for catchment-scale studies. Identifying alien vegetation through remote-sensing techniques and technologies is most likely the only means by which alien vegetation can be identified over large areas. The capacity to monitor invasions with this approach provides added incentive to develop means of identifying alien vegetation through a remote sensing approach. This study was unable to establish reliable spectral approaches to identify alien vegetation. Moreover, visual identification is time-consuming and ineffective with many of the species because of their aesthetic similarity to indigenous vegetation when considered at a coarse resolution. A means of automatically delineating areas of alien vegetation would be of tremendous import to future biodiversity assessment in this area.
Cape inland salt pans and Cape vernal pools represent important ecosystems, particularly for amphibians and certain bird species. The study showed these features to be substantially underrepresented on Mucina, Rutherford & Powrie’s (2007) vegetation map. It is recommended that an effort be made to accurately map these features. Further, as these features are often surrounded by agricultural land it is urged that the impacts of agricultural practices on these areas be assessed.
While not described in detail in this report, rapid urban development is taking place along the coastal zone to the east of Velddrif. This coastal zone accommodates diverse and acutely sensitive ecosystems and owing to their aesthetic appeal the zone is often subjected to intensive development (Palmer 2008). Little has been done to assess the impacts that development in this area have and will have on coastal ecosystems and the diverse assemblage of species that they support. It is consequently recommended that detailed research be done on the optimal management of this coastal area.
6.4 CONCLUSION
Biodiversity is a diverse concept that covers a range of entities over multiple spatial and temporal scales. Because of this it can be measured in many ways, each subject to its own unique set of advantages, shortcomings and assumptions. The relationship between biodiversity and land cover is complex and no doubt varies considerably depending on the context and the area in which it is assessed. This research has clearly shown the difficulty of positing simple cause-and- effect relationships between biodiversity and land-cover change. However, land-cover change provides an ideal platform from which to initiate more intensive analyses of biodiversity changes.
The most insightful conclusion that can be drawn from this study is that there is a need to develop more accurate and comprehensive monitoring systems for biodiversity in South Africa and especially in the CFR. Large gaps exist in our capacity to translate changes in land cover into changes in biodiversity at all levels of biological organization and to devise conservation and management plans in the light of these impacts. If the myriad challenges that face human societies at the dawn of the 21st century, such as increased pressure on a finite natural resource base associated with population growth and socio-economic development, anthropogenic climate change and rapidly escalating biodiversity loss, are to be adequately mitigated, a robust understanding of the relationship between land cover and biodiversity is not only essential but will likely prove crucial to our future well-being.
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